diff --git a/README.md b/README.md
index 7373e96f..54da3d0f 100644
--- a/README.md
+++ b/README.md
@@ -191,6 +191,10 @@ Cloud as an output for use in future steps in the workflow. These options only
 apply to ID tokens generated by this action. By default, this action does not
 generate any tokens.
 
+> [!CAUTION]
+>
+> ID Tokens have a maximum lifetime of 10 minutes. This value cannot be changed.
+
 -   `service_account`: (Required) Email address or unique identifier of the
     Google Cloud service account for which to generate the ID token. For
     example: